Emit header in MsgUpdateClient events (#8624)

* emit header in update client msg

* update CHANGELOG

* update spec

* fix nil header bug

* use JSON encoding for emitting header

* Update x/ibc/core/spec/06_events.md

* use proto for encoding

* add tests

* encode to hex before emitting header in event

* add comment addressing reasoning for hex encoding

* Update CHANGELOG.md

Co-authored-by: Federico Kunze <31522760+fedekunze@users.noreply.github.com>

Co-authored-by: Alessio Treglia <alessio@tendermint.com>
Co-authored-by: Federico Kunze <31522760+fedekunze@users.noreply.github.com>

CHANGELOG.md

@@ -70,6 +70,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * (x/ibc) [\#7949](https://github.com/cosmos/cosmos-sdk/issues/7949) Standardized channel `Acknowledgement` moved to its own file. Codec registration redundancy removed. 
 * (crypto/types) [\#8600](https://github.com/cosmos/cosmos-sdk/pull/8600) `CompactBitArray`: optimize the `NumTrueBitsBefore` method and add an `Equal` method.
 * (store/cachekv), (x/bank/types) [\#8719](https://github.com/cosmos/cosmos-sdk/pull/8719) algorithmically fix pathologically slow code
+* (x/ibc) [\#8624](https://github.com/cosmos/cosmos-sdk/pull/8624) Emit full header in IBC UpdateClient message.
 
 ### Bug Fixes
 

x/ibc/core/02-client/keeper/client.go

@@ -1,6 +1,8 @@
 package keeper
 
 import (
+	"encoding/hex"
+
 	"github.com/armon/go-metrics"
 
 	"github.com/cosmos/cosmos-sdk/telemetry"
@@ -95,6 +97,16 @@ func (k Keeper) UpdateClient(ctx sdk.Context, clientID string, header exported.H
 		)
 	}()
 
+	// emit the full header in events
+	var headerStr string
+	if header != nil {
+		// Marshal the Header as an Any and encode the resulting bytes to hex.
+		// This prevents the event value from containing invalid UTF-8 characters
+		// which may cause data to be lost when JSON encoding/decoding.
+		headerStr = hex.EncodeToString(types.MustMarshalHeader(k.cdc, header))
+
+	}
+
 	// emitting events in the keeper emits for both begin block and handler client updates
 	ctx.EventManager().EmitEvent(
 		sdk.NewEvent(
@@ -102,6 +114,7 @@ func (k Keeper) UpdateClient(ctx sdk.Context, clientID string, header exported.H
 			sdk.NewAttribute(types.AttributeKeyClientID, clientID),
 			sdk.NewAttribute(types.AttributeKeyClientType, clientState.ClientType()),
 			sdk.NewAttribute(types.AttributeKeyConsensusHeight, consensusHeight.String()),
+			sdk.NewAttribute(types.AttributeKeyHeader, headerStr),
 		),
 	)
 

x/ibc/core/02-client/keeper/client_test.go

@@ -1,6 +1,7 @@
 package keeper_test
 
 import (
+	"encoding/hex"
 	"fmt"
 	"time"
 
@@ -589,3 +590,39 @@ func (suite *KeeperTestSuite) TestCheckMisbehaviourAndUpdateState() {
 		})
 	}
 }
+
+func (suite *KeeperTestSuite) TestUpdateClientEventEmission() {
+	clientID, _ := suite.coordinator.SetupClients(suite.chainA, suite.chainB, exported.Tendermint)
+	header, err := suite.chainA.ConstructUpdateTMClientHeader(suite.chainB, clientID)
+	suite.Require().NoError(err)
+
+	msg, err := clienttypes.NewMsgUpdateClient(
+		clientID, header,
+		suite.chainA.SenderAccount.GetAddress(),
+	)
+
+	result, err := suite.chainA.SendMsgs(msg)
+	suite.Require().NoError(err)
+	// first event type is "message"
+	updateEvent := result.Events[1]
+
+	suite.Require().Equal(clienttypes.EventTypeUpdateClient, updateEvent.Type)
+
+	// use a boolean to ensure the update event contains the header
+	contains := false
+	for _, attr := range updateEvent.Attributes {
+		if string(attr.Key) == clienttypes.AttributeKeyHeader {
+			contains = true
+
+			bz, err := hex.DecodeString(string(attr.Value))
+			suite.Require().NoError(err)
+
+			emittedHeader, err := types.UnmarshalHeader(suite.chainA.App.AppCodec(), bz)
+			suite.Require().NoError(err)
+			suite.Require().Equal(header, emittedHeader)
+		}
+
+	}
+	suite.Require().True(contains)
+
+}

x/ibc/core/02-client/types/encoding.go

@@ -57,7 +57,7 @@ func MustUnmarshalConsensusState(cdc codec.BinaryMarshaler, bz []byte) exported.
 	return consensusState
 }
 
-// MustMarshalConsensusState attempts to encode an ConsensusState object and returns the
+// MustMarshalConsensusState attempts to encode a ConsensusState object and returns the
 // raw encoded bytes. It panics on error.
 func MustMarshalConsensusState(cdc codec.BinaryMarshaler, consensusState exported.ConsensusState) []byte {
 	bz, err := MarshalConsensusState(cdc, consensusState)
@@ -68,12 +68,12 @@ func MustMarshalConsensusState(cdc codec.BinaryMarshaler, consensusState exporte
 	return bz
 }
 
-// MarshalConsensusState protobuf serializes an ConsensusState interface
+// MarshalConsensusState protobuf serializes a ConsensusState interface
 func MarshalConsensusState(cdc codec.BinaryMarshaler, cs exported.ConsensusState) ([]byte, error) {
 	return cdc.MarshalInterface(cs)
 }
 
-// UnmarshalConsensusState returns an ConsensusState interface from raw encoded clientState
+// UnmarshalConsensusState returns a ConsensusState interface from raw encoded consensus state
 // bytes of a Proto-based ConsensusState type. An error is returned upon decoding
 // failure.
 func UnmarshalConsensusState(cdc codec.BinaryMarshaler, bz []byte) (exported.ConsensusState, error) {
@@ -84,3 +84,30 @@ func UnmarshalConsensusState(cdc codec.BinaryMarshaler, bz []byte) (exported.Con
 
 	return consensusState, nil
 }
+
+// MarshalHeader protobuf serializes a Header interface
+func MarshalHeader(cdc codec.BinaryMarshaler, h exported.Header) ([]byte, error) {
+	return cdc.MarshalInterface(h)
+}
+
+// MustMarshalHeader attempts to encode a Header object and returns the
+// raw encoded bytes. It panics on error.
+func MustMarshalHeader(cdc codec.BinaryMarshaler, header exported.Header) []byte {
+	bz, err := MarshalHeader(cdc, header)
+	if err != nil {
+		panic(fmt.Errorf("failed to encode header: %w", err))
+	}
+
+	return bz
+}
+
+// UnmarshalHeader returns a Header interface from raw proto encoded header bytes.
+// An error is returned upon decoding failure.
+func UnmarshalHeader(cdc codec.BinaryMarshaler, bz []byte) (exported.Header, error) {
+	var header exported.Header
+	if err := cdc.UnmarshalInterface(bz, &header); err != nil {
+		return nil, err
+	}
+
+	return header, nil
+}

x/ibc/core/02-client/types/encoding_test.go

@@ -0,0 +1,30 @@
+package types_test
+
+import (
+	"github.com/cosmos/cosmos-sdk/x/ibc/core/02-client/types"
+	ibctmtypes "github.com/cosmos/cosmos-sdk/x/ibc/light-clients/07-tendermint/types"
+)
+
+func (suite *TypesTestSuite) TestMarshalHeader() {
+
+	cdc := suite.chainA.App.AppCodec()
+	h := &ibctmtypes.Header{
+		TrustedHeight: types.NewHeight(4, 100),
+	}
+
+	// marshal header
+	bz, err := types.MarshalHeader(cdc, h)
+	suite.Require().NoError(err)
+
+	// unmarshal header
+	newHeader, err := types.UnmarshalHeader(cdc, bz)
+	suite.Require().NoError(err)
+
+	suite.Require().Equal(h, newHeader)
+
+	// use invalid bytes
+	invalidHeader, err := types.UnmarshalHeader(cdc, []byte("invalid bytes"))
+	suite.Require().Error(err)
+	suite.Require().Nil(invalidHeader)
+
+}

x/ibc/core/02-client/types/events.go

@@ -12,6 +12,7 @@ const (
 	AttributeKeySubjectClientID = "subject_client_id"
 	AttributeKeyClientType      = "client_type"
 	AttributeKeyConsensusHeight = "consensus_height"
+	AttributeKeyHeader          = "header"
 )
 
 // IBC client events vars

x/ibc/core/spec/06_events.md

@@ -32,6 +32,7 @@ callbacks to IBC applications.
 | update_client | client_id        | {clientId}        |
 | update_client | client_type      | {clientType}      |
 | update_client | consensus_height | {consensusHeight} |
+| update_client | header           | {header}          |
 | message       | action           | update_client     |
 | message       | module           | ibc_client        |
 
@@ -238,4 +239,3 @@ callbacks to IBC applications.
 | message        | action                   | timeout_packet       |
 | message        | module                   | ibc-channel          |
 
-